1. Field of the Invention
This invention relates to a substrate heating apparatus for heating a substrate under a vacuum pressure, and to a multi-chamber substrate processing system for processing a substrate under a vacuum pressure.
2. Description of the Related Art
Electronic parts such as semiconductor devices, e.g., memories and processors, all kinds of circuit elements, and sensing element are often manufactured via lots of surface processes onto board-shaped objects as bases of products, which are hereinafter called “substrates”. Such a surface processes has been well known as surface denaturalizing, e.g., surface oxidation, thin-film deposition, or circuit formation process, e.g., etching. In addition, substrate heating process has been often carried out on various purposes. For example, pre-heating of a substrate has been carried out for degassing prior to thin-film deposition. Annealing of a substrate has been carried out after thin-film deposition or ion implantation. Baking of a substrate has been carried out before or after light exposure of photoresist.
A substrate heating apparatus used for such a heating process often has a structure where a substrate is heated under a vacuum pressure. This is because heating under atmospheric pressure highly probably brings the problem that moisture, oxygen or other contaminant is incorporated into the substrate. Heating under a vacuum pressure is carried out in an air-tight vessel, i.e., vacuum chamber, placing a substrate therein.
Prior-art substrate heating apparatuses will be described, referring to FIGS. 6 and 7. FIG. 6 is the schematic front cross-sectional view of a prior-art heating apparatus. FIG. 7 is the schematic front cross-sectional view of another prior-art heating apparatus. The apparatus shown in FIG. 6 is built in a so called cluster-tool-type system. “Cluster tool” is the general term for a vacuum processing system where a transfer chamber comprising a transfer robot therein is provided centrally, and a load-lock chamber and process chambers are connected with the transfer chamber at the periphery. In FIG. 6, the load-lock chamber 83 is the vacuum chamber where the substrate 9 is temporarily stored while it is transferred from the atmospheric outside to one of the process chambers 82. The system comprises a vacuum chamber called “unload-lock chamber” (not shown), in which the substrate 9 is stored while it is transferred out from one of the process chambers 82 to the atmospheric outside. The load-lock chamber 83 is occasionally used commonly for the unload-lock chamber.
The heating apparatus shown in FIG. 6 comprises a heat chamber, which is one of the process chambers 82. A heat stage 821 is provided in the heat chamber 82. An elevation mechanism 822 is provided outside the heat chamber 82 so that the heat chamber 82 can be elevated up and down. Through holes are provided vertically penetrating the heat stage 821. Transfer pins 823 are inserted into the through holes respectively. For example, three through holes are provided, and three transfer pins 823 are inserted respectively.
A heater 824 is provided in the heat stage 821. The substrate 9 stored in the load-lock chamber 83 by an auto loader (not shown) is then transferred to the heat chamber 82 by the transfer robot 811. The heat stage 821 is located at a lower position on standby. In this state, the upper ends of the transfer pins 823 project over the heat stage 821.
The substrate 9 is passed from the transfer robot 811 onto the transfer pins 823. Afterward, the heat stage 821 is elevated up by the elevation mechanism 822. As a result, the substrate 9 is placed on the heat stage 821, being heated thereby. After heating the substrate 9 for a required period, the heat stage 821 is elevated down, placing the substrate 9 on the transfer pins 823 again. Afterward, the transfer robot 81 transfers the heated substrate 9 out of the heat chamber 82 to the load-lock chamber 83. Then, the substrate 9 is transferred out to the atmospheric outside by the auto loader.
The system shown in FIG. 7 comprises a means for heating a substrate 9 in a load-lock chamber 83. An opening is provided in the upper wall of the load-lock chamber 83. A transparent window 831 is air-tightly fitted in the opening. A lamp heater 833 is provided outside the transparent window 831. Radiant rays from the lamp heater 833 illuminate the substrate through the transparent window 831, heating the substrate 9 thereby. After heating, the substrate 9 is processed in a process chamber 84.
In heating a substrate generally, it is effective to make the substrate contact onto a hot body, i.e., to utilize heat transfer by conduct. The heating apparatus shown in the FIG. 6 belongs to this type. In this type, however, when the hot body is exposed to the atmosphere, the surface of the body would be oxidized; otherwise dusts or other contaminants thermally adhere to the body. As a result, particles contaminating the substrate would be produced from the body.
Therefore, it is preferable to dispose such a hot body for heating in an atmosphere of a vacuum pressure normally. The apparatus shown in FIG. 6 comprises the chamber 82 solely used for the heating, to which the load-lock chamber 83 is connected via the transfer chamber 81 with the continuous vacuum environment. The environment in the load-lock chamber 83 is alternately converted to the atmosphere and vacuum, which is accompanied by the transfer-in-and-out of the substrate 9. On the other hand, the heat chamber 82 is kept at a vacuum pressure normally, because the transfer valve 825 is closed for isolation while the load-lock chamber 83 is opened to the atmosphere.
The above-described structure of the apparatus shown in FIG. 6 enables disposition of the hot heat stage 821 in the vacuum environment normally. However, the apparatus shown in FIG. 6 has the demerit that the number of the chambers increases, that is, the apparatus is larger-scaled. This brings the problem of increasing the cost and the occupation space of the apparatus. In addition, respecting to productivity it brings the problem of decreasing the total process efficiency because more time is needed for transferring the substrate.
On the other hand, the apparatus shown in FIG. 7 does not bring the above-described problem of the contamination, because the radiation heating is employed, disposing the lamp heater 832 outside the load-lock chamber 83. However, the radiation heating has the difficulty in making radiating ray density distribution, i.e., illumination distribution, sufficiently uniform on the surface of the substrate. It means in-plane uniformity of the heating is not sufficient. In addition, in the case it is required to heat a glass substrate, which typically happens in manufacturing a display device such as liquid crystal display and plasma display, efficiency can not be expected for the heating because radiating rays are not absorbed in the substrate but pass through it.
Moreover, the radiation heating has the problem of dependency on the surface state of a substrate. In the case a film of high reflectivity is coated on the right surface of a substrate, for example, heat efficiency would decrease much. As well, radiation absorption rate depends on the surface state of a substrate. For example, it changes depending on a rugged surface by etching or a mirror-polished surface. Because the radiation heating depends on such factors as material of the substrate and surface state of the substrate, it has the difficulty in heating a substrate with high stability and reproducibility.